Melanoma is a cancer characterized by the uncontrolled growth of pigment-producing cells (melanocytes). Malignant melanoma develops from a neoplastic transformation of melanocytes, which are predominantly found in the basal layer of the epidermis and the eye. (Spagnolo F et al., Archives of Dermatology Research, 2012, 304: 177-184; Hurst E A et al., Archives of Dermatology Research, 2003, 139: 1067-1073). Malignant melanoma is the most aggressive form of skin cancer. In 2014, it is estimated that there will be 76,100 new cases of melanoma of the skin and an estimated 9,710 people will die of this disease. (SEER Stat Fact Sheets: Melanoma of the Skin, Surveillance Epidemiology and End Results Program,—accessed on Jun. 2, 2014 at http://seer.cancer.gov/statfacts/html/melan.html).
Although surgical removal of early melanoma lesions leads to a cure rate of 90%, advanced melanoma resists chemotherapy and tends to quickly metastasize (Spagnolo F et al., Archives of Dermatology Research, 2012, 304: 177-184); for these reasons, prognosis for advanced melanoma is poor, with 5-year survival rates of 78% for patients with stage IIIA, 59% for patients with stage IIIB, and 40% for patients with stage IIIC, respectively. (Balch C M et al., Journal of Clinical Oncology, 2009, 27(36): 6199-6206). For patients with distant metastases, the prognosis significantly worsens, with 1 year survival rates of 62% for stage M1a, 53% for stage M1b and only 33% for stage M1c. (Balch C M et al., Journal of Clinical Oncology, 2009, 27(36): 6199-6206).
The treatment options for metastatic melanoma are limited. Prior to 2011, only two therapies for metastatic melanoma had been approved by the FDA: dacarbazine and high dose interleukin 2 (“HD IL-2”), neither of which increased median overall survival. (Hill G et al., Cancer, 1984, 53:1299-1305; Atkins M et al., Journal of Clinical Oncology, 1999, 17(7): 2105-2116; Phan G et al., Journal of Clinical Oncology, 2001, 19(15): 3477-3482). Moreover, dacarbazine is limited by a low response rate of 10% to 15%, while HD IL-2 has an even lower response rate of 6% to 10%. (Finn L et al., BMC Medicine, 2012, 10:23). During 2011, the FDA approved two more therapies for advanced melanoma, vemurafenib (Zelboraf™) and ipilimumab. (Finn L et al., BMC Medicine, 2012, 10:23). While vemurafenib has demonstrated good clinical activity with a high response rate and low toxicity, its applicability is limited to the 40%-60% of melanoma patients who harbor an activating mutation in the BRAF gene that leads to constitutive activation of the mitogen-activated protein kinase pathway (“MAPK”), which causes increased cellular proliferation as well as increased oncogenic activity. (Finn L et al., BMC Medicine, 2012, 10:23). Additionally, most patients who initially respond to treatment with BRAF inhibitors relapse, indicating the development of drug resistance and demonstrating the limitations of targeting only one pathway to eradicate melanoma. (Villanueva J et al., Cancer Cell, 2010, 18(6): 683-695; Spagnolo F et al., Archives of Dermatology Research, 2012, 304: 177-184). Ipilmumab can induce long-term responses in a subset of patients, but its utility is limited by its low response rate of 10% to 15% and by the fact that it improves median survival time by only two months. (Finn L et al., BMC Medicine, 2012, 10:23). Thus, there remains a serious need for additional therapies for treatment of melanoma.
Citation or identification of any reference in Section 2 of this application is not to be construed as an admission that the reference is prior art to the present application.